Initial commit

Author: colin-passiv

.gitignore

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+.project
+target

README.md

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+# Embed
+
+Scala macro for embedding file content directly into a scala source file at compile time.
+
+## Usage
+
+first import the macro:
+```scala
+import com.passivsystems.embed.Embed._
+```
+
+then can reference any file with a path relative to the current source file:
+```scala
+val text: String = embed("resource.txt")
+```
+
+## String interpolation
+
+By using the ```sEmbed```, we can have similar semantics to ```s""``` String interpolation. The embedded file can refer to any variable in scope at the point of call.
+
+Note, that the curly braces are required for all embedded expressions. e.g. ```${myVal}``` not ```$myVal```
+
+e.g.
+```scala
+val guard = true
+val txt = sEmbed("template.txt")
+```
+where template.txt:
+```
+the guard is: ${if (guard) "TRUE" else "FALSE"}
+```
+
+## Scala js
+
+One possible usecase is in Scala js projects to move html into their own file.
+e.g.
+
+```scala
+import org.scalajs.dom
+def el[T <: dom.raw.Element](id: String) =
+    dom.document.getElementById(id).asInstanceOf[T]
+
+val btnId = "uniqueId"
+// el[dom.raw.HTMLElement]("div").innerHTML = s"""
+// <button id="${btnId}">Click me</button>
+// """
+el[dom.raw.HTMLElement]("div").innerHTML = sEmbed("status.html")
+el[dom.raw.HTMLButtonElement](btnId).onclick = { event: MouseEvent => println("Clicked!") }
+```
+where status.html:
+```html
+<button id="${btnId}">Click me</button>
+```

build.sbt

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+organization := "com.passivsystems"
+
+name := "embed"
+
+version := "0.0.1"
+
+scalaVersion :=  "2.11.7"
+
+libraryDependencies <+= scalaVersion("org.scala-lang" % "scala-reflect" % _)  // for scala macro

src/main/scala/Embed.scala

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+package com.passivsystems.embed
+
+package object Embed {
+  import scala.language.experimental.macros
+
+  /** Embeds file content directly into source at compile time.
+    *
+    * The content file is a path relative to the source file.
+    */
+  def embed (path: String): String = macro Embed.embed
+
+  /** Embeds file content and string interpolates it at compile time.
+    *
+    * The content file is a path relative to the source file.
+    *
+    * Note: the curly braces are required, and only simple identifier expressions are supported.
+    * e.g. {{{ ${myVal} }}}
+    *
+    * {{{
+    *   val divId = "uniqueId"
+    *   val html = sEmbed("status.html")
+    * }}}
+    * Where status.html (in same directory):
+    * {{{
+    * <div id="${divId}">Div content</div>
+    * }}}
+    */
+  def sEmbed(path: String): String = macro Embed.sEmbed
+
+  private[this] object Embed {
+    import scala.reflect.macros.blackbox.Context
+
+    def embed(c: Context)(path: c.Expr[String]): c.Expr[String] = {
+      import c.universe._
+      embedImpl(c)(path, false)
+    }
+
+    def sEmbed(c: Context)(path: c.Expr[String]): c.Expr[String] = {
+      import c.universe._
+      embedImpl(c)(path, true)
+    }
+
+    def embedImpl(c: Context)(path: c.Expr[String], interpolate: Boolean): c.Expr[String] = {
+      import c.universe._
+
+      val q"${pathConst: String}" = path.tree
+
+      val pos = path.tree.pos
+      val currentDirectory = pos.source.file.file.getAbsoluteFile.getParentFile
+      val rawContent = contentOf(currentDirectory, pathConst)
+
+      if (interpolate) interpolateExpr(c)(rawContent)
+      else             constantExpr(c)(rawContent)
+    }
+
+    def contentOf(currentDirectory: java.io.File, path: String) = {
+      val source = scala.io.Source.fromFile(new java.io.File(currentDirectory, path))
+      val content = source.mkString
+      source.close()
+      content
+    }
+
+    def interpolateExpr(c: Context)(content: String): c.Expr[String] = {
+      import c.universe._
+      val parts = content.split("\\$\\{([^\\}]*)\\}").toSeq
+      val args = "\\$\\{([^\\}]*)\\}".r.findAllMatchIn(content).map(_.group(1)).map(c.parse(_)).toSeq
+      c.Expr[String](q"scala.StringContext(..$parts).s(..$args)")
+    }
+
+    def constantExpr(c: Context)(content: String): c.Expr[String] = {
+      import c.universe._
+      c.Expr[String](q"$content")
+    }
+  }
+}